Carbon-12 (C-12) is selected as the standard element to determine the relative atomic mass of other elements because it has several desirable properties that make it suitable for this purpose. These properties include:
Abundance: Carbon-12 is the most abundant stable isotope of carbon, constituting approximately 98.93% of naturally occurring carbon. Its high abundance ensures that there is a significant amount available for measurement and analysis.
Stability: Carbon-12 is a stable isotope, meaning it does not undergo radioactive decay. This stability allows for accurate and consistent measurements over time, making it a reliable reference isotope.
Mass value: Carbon-12 has a mass of exactly 12 atomic mass units (amu) defined as 1/12th the mass of a carbon-12 atom. This value is assigned by definition, providing a consistent baseline for comparing the atomic masses of other elements.
Similar chemical behavior: Carbon-12 shares similar chemical properties and behaviors with other isotopes of carbon. This similarity allows for easier comparisons and ensures that the reference isotope represents the average behavior of the element.
By selecting carbon-12 as the standard reference isotope, scientists can establish a unified scale for relative atomic masses. The relative atomic mass of other elements is then determined by comparing the masses of their isotopes relative to the mass of carbon-12. This standardization enables accurate and consistent measurements across different laboratories and research studies, facilitating communication and understanding in the field of chemistry.